The FDA has come into conflict with Congressional investigators over its refusal to release information on which Chinese companies supplied a tainted blood thinner that has led to at least 81 deaths in the United States.

Earlier this year, the FDA issued its first alert over tainted supplies of the blood thinner heparin. To date, the contaminated drug has caused allergic reactions that have led to more than 1,000 adverse events in the United States, including 81 confirmed deaths since January 2007. The tainted drugs have also been detected in 10 other countries.

In spite of the original warning, the FDA recently discovered that tainted heparin was still on the shelves in some California hospitals. In response, the alert was widened to include hospitals, physicians groups and pharmaceutical organizations.

“We found it on crash carts, catheter labs, and even on one hospital pharmacist’s shelf,” said Karen Riley of the FDA.

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Heparin is a widely used blood thinner, frequently given in large doses to patients in order to prevent clotting during complex medical procedures such as kidney dialysis or heart surgery. In 2007, then-lead heparin manufacturer Baxter International made $30 million in sales of the drug.

A d v e r t i s e m e n t

Most of the heparin sold in the United States is manufactured from ingredients made in China, a major supplier of drug ingredients to the United States. According to Baxter Chairman and Chief Executive Robert Parkinson, China is a favored source for heparin in particular, because “that’s where the pig population is.”

The active ingredient in heparin is derived from pig intestines, and China has five times the pig population of the United States.

The FDA suspects that the deadly heparin originally became contaminated in a Chinese factory, but has refused to tell Congress which companies supplied heparin ingredients to the United States from China. The agency says that confidentiality agreements with the producers bar it from revealing any of their names.

The FDA has determined that the tainted heparin was adulterated with a heparin-like chemical called oversulfated chondroitin sulfate, derived from shellfish. The presence of this synthetic chemical suggests that the drugs were deliberately tampered with during the manufacturing process, probably to decrease costs for the supplier. But the FDA does not yet know at what stage in the manufacturing process the chemical was added.